project.py: Support project options

  o Load the option definitions with the OptionPool

  o Set the user selected project option values according to the passed Context

  o Process conditionals in the loaded project configuration,
    excepting for the project name and actual option definitions

  o Removed a lot of examples from the default config.

    This is getting moved into more structured documentation, and the
    default config is only presented to the user beside the documentation
    which describes what each thing means.

1 files changed, 47 insertions, 30 deletions

diff --git a/buildstream/project.py b/buildstream/project.py
index dcf1c1e1f..d3d8dc525 100644
--- a/buildstream/project.py
+++ b/buildstream/project.py
@@ -37,6 +37,7 @@ from . import _yaml
 from . import _loader  # For resolve_arch()
 from ._profile import Topics, profile_start, profile_end
 from . import LoadError, LoadErrorReason
+from ._options import OptionPool
 
 BST_FORMAT_VERSION = 0
 """The base BuildStream format version
@@ -60,17 +61,11 @@ _ALIAS_SEPARATOR = ':'
 
 
 class Project():
-    """Project Configuration
+    """Project()
 
-    Args:
-       directory (str): The project directory
-       host_arch (str): Symbolic host machine architecture name
-       target_arch (str): Symbolic target machine architecture name
-
-    Raises:
-       :class:`.LoadError`
+    The Project Configuration
     """
-    def __init__(self, directory, host_arch, target_arch=None):
+    def __init__(self, directory, context):
 
         self.name = None
         """str: The project name"""
@@ -81,16 +76,16 @@ class Project():
         self.element_path = None
         """str: Absolute path to where elements are loaded from within the project"""
 
-        self._variables = {}    # The default variables overridden with project wide overrides
-        self._environment = {}  # The base sandbox environment
-        self._elements = {}     # Element specific configurations
-        self._aliases = {}      # Aliases dictionary
-        self._workspaces = {}   # Workspaces
+        self._context = context  # The invocation Context
+        self._variables = {}     # The default variables overridden with project wide overrides
+        self._environment = {}   # The base sandbox environment
+        self._elements = {}      # Element specific configurations
+        self._aliases = {}       # Aliases dictionary
+        self._workspaces = {}    # Workspaces
         self._plugin_source_paths = []   # Paths to custom sources
         self._plugin_element_paths = []  # Paths to custom plugins
+        self._options = None    # Project options, the OptionPool
         self._cache_key = None
-        self._host_arch = host_arch
-        self._target_arch = target_arch or host_arch
         self._source_format_versions = {}
         self._element_format_versions = {}
 
@@ -137,12 +132,12 @@ class Project():
         variables = _yaml.node_get(config, Mapping, 'variables')
         variables['max-jobs'] = multiprocessing.cpu_count()
 
-        variables['bst-host-arch'] = self._host_arch
-        variables['bst-target-arch'] = self._target_arch
+        variables['bst-host-arch'] = self._context.host_arch
+        variables['bst-target-arch'] = self._context.target_arch
 
         # This is kept around for compatibility with existing definitions,
         # but we should probably remove it due to being ambiguous.
-        variables['bst-arch'] = self._host_arch
+        variables['bst-arch'] = self._context.host_arch
 
         # Load project local config and override the builtin
         project_conf = _yaml.load(projectfile)
@@ -154,25 +149,47 @@ class Project():
             'split-rules', 'elements', 'plugins',
             'aliases', 'name',
             'arches', 'host-arches',
-            'artifacts',
+            'artifacts', 'options',
         ])
 
+        # The project name, element path and option declarations
+        # are constant and cannot be overridden by option conditional statements
+        self.name = _yaml.node_get(config, str, 'name')
+        self.element_path = os.path.join(
+            self.directory,
+            _yaml.node_get(config, str, 'element-path', default_value='.')
+        )
+
+        # Load project options
+        options_node = _yaml.node_get(config, Mapping, 'options', default_value={})
+        self._options = OptionPool(self.element_path)
+        self._options.load(options_node)
+
+        # Collect option values specified in the user configuration
+        overrides = self._context._get_overrides(self.name)
+        override_options = _yaml.node_get(overrides, Mapping, 'options', default_value={})
+        self._options.load_values(override_options, self._context._cli_options)
+
+        # We're done modifying options, now we can use them for substitutions
+        self._options.resolve()
+
+        #
+        # Now resolve any conditionals in the remaining configuration,
+        # any conditionals specified for project option declarations,
+        # or conditionally specifying the project name; will be ignored.
+        #
+        self._options.process_node(config)
+
         # Resolve arches keyword, project may have arch conditionals
-        _loader.resolve_arch(config, self._host_arch, self._target_arch)
+        _loader.resolve_arch(config, self._context.host_arch, self._context.target_arch)
 
         #
         # Now all YAML composition is done, from here on we just load
         # the values from our loaded configuration dictionary.
         #
 
-        self.name = _yaml.node_get(config, str, 'name')
-        self.element_path = os.path.join(
-            self.directory,
-            _yaml.node_get(config, str, 'element-path')
-        )
-
         # Load artifacts pull/push configuration for this project
-        artifacts = _yaml.node_get(config, Mapping, 'artifacts')
+        artifacts = _yaml.node_get(config, Mapping, 'artifacts', default_value={})
         _yaml.node_validate(artifacts, ['pull-url', 'push-url', 'push-port'])
         self.artifact_pull = _yaml.node_get(artifacts, str, 'pull-url', default_value='') or None
         self.artifact_push = _yaml.node_get(artifacts, str, 'push-url', default_value='') or None
@@ -182,11 +199,11 @@ class Project():
         self._workspaces = self._load_workspace_config()
 
         # Version requirements
-        versions = _yaml.node_get(config, Mapping, 'required-versions')
+        versions = _yaml.node_get(config, Mapping, 'required-versions', default_value={})
         _yaml.node_validate(versions, ['project', 'elements', 'sources'])
 
         # Assert project version first
-        format_version = _yaml.node_get(versions, int, 'project')
+        format_version = _yaml.node_get(versions, int, 'project', default_value=0)
         if BST_FORMAT_VERSION < format_version:
             major, minor = utils.get_bst_version()
             raise LoadError(